File No. 3921-46

CIVIL AERONAUTICS BOARD

ACCIDENT INVESTIGATION REPORT

Adopted: March 25, 1948    Released: March 29, 1948

NEAR CHRISTIANSBURG, VIRGINIA, OCTOBER 20, 1946

Pilot Harry C. Hippert and two revenue passengers, Drs Preston Burton and Gilbert Burton, were killed October 20, 1946, when their plane crashed against a fog-covered mountain near Christiansburg, Virginia. The 7W Spartan, NC 58300, owned by Lynchburg Air Transport and Sales Corporation, was destroyed by impact and fire. It was equipped for instrument flight. Hippert was a commercial pilot rated to fly single and multiengine land planes but he was not rated as an instrument pilot.

At the request of the Civil Aeronautics Board the initial investigation of this Accident was made by a Civil Aeronautics Administration Inspector. On the basis of this investigation a statement of facts, conditions and circumstances was issued by the Board on December 20, 1946. Subsequently, upon request of the aircraft owner who believed engine fire had occurred in flight, and Air Safety Investigator and the Board's Powerplant Specialist were dispatched for a personal investigation and inspection of the salvaged engine. The following report is based on their findings.

The pilot and his two passengers took off from Roanoke, Virginia, at 0915 on a cross-country flight to South Dakota. No flight plan was filed. Weather Conditions at the time, as reported to the pilot, were Roanoke-ceiling 1,200 feet visibility 5 miles, light rain, light fog, Pulaski, Virginia-ceiling 500 feet, overcast 2,000 feet, visibility 3 miles, light fog. Two mountain ranges to be crossed between Roanoke and Pulaski rise to an elevation of approximately 3,000 feet. The plan was later observed flying extremely low over Highway 11 in a westerly direction, and at a point about 4 miles east of Christiansburg it was seen entering the overcast in a climbing attitude. Shortly thereafter it collided with a tree atop the fog-shrouded Christiansburg mountain and burned. The engine separated from the aircraft on impact and came to rest in an inverted position with its carburetor and associated parts on the top side.

No evidence was found to indicate that there had been a fire in flight, nor was anything disclosed which varied from the report filed by the Civil Aeronautics Administration Inspector The last known witness to the flight prior to the time the plane entered the overcast stated that the engine sounded normal and that he saw no indication of fire. Investigation disclosed the possibility that a slight flash fire of less than one minute's duration occurred to the engine immediately subsequent to the crash, which would account for the flame impingement found on the carburetor hot air control box unit. There was no melting of any of the aluminum ducting, rivets or solder in or adjacent to the induction system, nor were there any indications that the soldered carburetor intake screen or impeller vanes had been subjected to excessive heat, as would have been the condition had any high intensity fire occurred in flight.

Upon the basis of all available evidence, the Board concludes that the probable cause of this accident was the pilot's attempt to continue visual flight into instrument weather over mountainous terrain.

BY THE CIVIL AERONAUTICS BOARD

/s/ OSWALD RYAN

s/ HARLLEE BRANCH

/s/ JOSH LEE